Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5174,6 +5174,8 @@
   "%select{struct|interface|union|class|enum}1">;
 def err_flexible_array_has_nontrivial_dtor : Error<
   "flexible array member %0 of type %1 with non-trivial destruction">;
+def err_flexible_array_in_objc_class : Error<
+  "%0 may not be used in interface due to flexible array member">;
 def ext_flexible_array_in_struct : Extension<
   "%0 may not be nested in a struct due to flexible array member">,
   InGroup<FlexibleArrayExtensions>;
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -14989,6 +14989,12 @@
         // Ivars can not have abstract class types
         FD->setInvalidDecl();
       }
+      if (isa<ObjCContainerDecl>(EnclosingDecl) && FDTTy->getDecl()->hasFlexibleArrayMember()) {
+        Diag(FD->getLocation(), diag::err_flexible_array_in_objc_class)
+          << FD->getDeclName();
+        FD->setInvalidDecl();
+        EnclosingDecl->setInvalidDecl();
+      }
       if (Record && FDTTy->getDecl()->hasObjectMember())
         Record->setHasObjectMember(true);
       if (Record && FDTTy->getDecl()->hasVolatileMember())
Index: clang/test/SemaObjC/ivar-sem-check-3.m
===================================================================
--- /dev/null
+++ clang/test/SemaObjC/ivar-sem-check-3.m
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -emit-llvm-only -fobjc-arc -verify -Wno-objc-root-class %s
+
+// Test using structs with flexible array member as ivars.
+struct Packet
+{
+  unsigned int size;
+  char data[];
+};
+
+@interface INTF_FLEXIBLE_ARRAY_MEMBER
+{
+  // Pointer to a struct with flexible array member is acceptable.
+  struct Packet *packetPtr;
+  struct Packet packet;  // expected-error {{'packet' may not be used in interface due to flexible array member}}
+}
+@end
+// Implementation to trigger ivar layout.
+@implementation INTF_FLEXIBLE_ARRAY_MEMBER
+@end